Rotor for ultracentrifuge machines



. Au 17, 1948. J. GREIBMEIIER 7,33

ROTOR FOR ULTRA CENTRIFUGE MACHINES Filed May 16, 1946 Patented Aug. 17, 1948 UNITED STATES PATENT OFFICE 2,447,330 I ROTOR FOR ULTRACENTRIFUGE MACHINES 7 Joseph Grebnieier, Menlo Park, Calif.

Application May 16, 1946, Serial No. 670,211

6 Claims. (01. 233-26) This invention relates to an ultra-centrifuge. Such devices as are now in general use comprise a rotor in the form of a substantially solid frustoconical metal block, slightly cored out at the upper end from which a plurality of circumferentially spaced cylindrical wells or cavities extend obliquely into the block. These wells are arranged to receive test tubes which carry the substance to be centrifuged. A removable top or lid is screwed or otherwise secured over the open top of the chambered rotor and serves, through the medium of an interposed gasket, to seal the chamber into which the open top tubes extend from interfering with the relatively high vacuum in which the rotor is operated.

The rotor, when in operation, is usually confined within a steel chamber having very thick walls which act as a guard in the event of breakdown or explosion of the rotor under strain casioned by the very high speed (1000 R. P. S.) at which these devices are rotated, to effect the centrifugation desired. v

The steel chamber for this purpose is usually provided with an air-sealing cover so that a high vacuum may be effected therein after placement of the tube-laden rotor therein. Such an organization permits rapid acceleration of the rotor and the high speed of rotation required. It also prevents generation of heat in the rotor.

Usually the rotor is supported by a fine steel shaft from which it is driven, the shaft having one end thereof removably connected to the rotor and the other end thereof operatively connected with a driving mechanism.

The tubes which contain the substance to be centrifuged are preferably constructed of stainless steel or plastic, as more fragile materials such as glass, would not stand the strain resulting from the centrifugal force produced under the high speed of rotation required. 7

The tube supporting wells or cavities in the rotor are disposed adjacent to and parallel with the conical wall of the rotor with the result that the axes of such cavities converge upwardly toward the axis of the rotor and the walls communicate with the chambered upper end of the rotor. Chambered rotors of this type now in use are provided with a detachable cover and the tubes which are carried in the rotor are, therefore, not provided with closures or cover means. .As a; result the open tubescannot be well filled with the substance to be treated due to their normally inclined supported positions in the rotor and the further fact that the surface of the substance in the tubes changes from a horizontal to a vertical position under centrifugal force. To the best of my knowledge, the rotors as now generally used are substantially solid except for the chambered upper end and the communicating tube receiving wells or cavities, as a result of which the rotors are of considerable weight even though they may be constructed of a light metal such as Duralumin, dow metal, or the like. For the usual size such rotors weigh seven to eight pounds.

It is important to note, therefore, that the retor must be operated at a very high speed of rotation (1000 R. P. S.) which is necessary for throwing small particles, such as virus, bacteria, or bacteriophage to the bottoms of the inclined supported tubes in the segregating of same from the liquid in which they are originally suspended.

Due to such high speed of rotation it is necessary that the rotors be constructed to withstand the strain occasioned by the centrifugal force exerted and that they also be capable of supporting the tubes in a way to avoid breakage thereof.

The rotorsabove referred to due to their substantial weight and accordingly high inertia,require 30 to 40 minutes in their acceleration from rest to maximum operating speed and a like interval of time for their deceleration from operating speed to rest, or a period of from one hour to one hour and 20 minutes for acceleration and deceleration. Since from one to two hour are required for a centrifuging operation, relatively few operations can be carried out in a day since the time used for acceleration and deceleration is lost so far as the actual centrifugating operation is concerned.

The connection of the driving shaft and rotor-above referred to, has been made with the cover or at least to a point at or adjacent the top of the rotor which is substantially above the center of mass thereof. This point of connection is not conducive to smooth running of A the rotor, which, particularly upon acceleration thereof is subject to more or less vibration in planes at right angles to the axis of the drive shaft.

g A primary object of this invention is the pro- 3 vision of a rotor for ultra-centrifugating machines which substantially overcomes the above noted objections.

A further object of the invention is the provision of a rotor for centrifugating machines which is of a single piece in the elimination of a cover, and wherein the substance supporting tubes are separately provided with lids, whereby they may be filled with the substance to be centrifugated.

A still further object of the invention is the rovision of a rotor for centrifugating machines which is in the-approved form-of the f-rusto-cone ical blocks of theeprior ,art, but which includesvertically spaced flanges or fins in the provision of intervening circumferentially extending g slots whereby the rotor is r endered relatively while haVing-s-uificient tensile strength to withstand the strain occasionedby light in weight centrifugal force in operation.

A still further object of theinventioni's 'thetiai provision in a centrifugating machine of a,frustoconical rotor and a drive shaft having a drivingconnection, with the rotor body directly and at a' pointrsubstantially below the upper end thereofzwhereby to avoid vibrationon -ac celeration and insure smoother running of the rotor inoperation'," 0 With' the 'above o bjects inrview r-together with others that will present themselves-in the course of thefollowing'descriptiomreference will be had tofth'e accompanying drawing wherein is illustrat'ed'a preferred embodiment of the invention, and"wherein--e Fig: 1 is a fragmental perspectiveview showing' the installationof the improved rotor to ;-a ;s tand-; ard'ultra-centrifugal machine, the rotor being suspendedabove the vacuum chamber in normal oper iveo it on; 1. 1 t r ,r i Fig. 2 is a'verticalsectional view of therotor and drive'shaft connection therewith as observed in theplane of line 2'j2, Fig.1,3; "Fig. 3 is atopplan view'of theldrive shaft in .transversesectiom jFig. dis ,a view showing one of the e h substances containing ,tub e's, invertical amal section, a lid therefor in side elevation, and a lid retaining nut mtransverse s ection.

Referring now, in detail t of reference characters, l0 designates the improved rotor, which ,in use i is rotatively supported in a thick walledsteelchamberC lliig, l) which the rotor showing the re enerates lati n to --the material inltheblock be so disposed as to withof substantially frusto-conical form. The block is provided with a plurality (Nos. 8, 10, or 12) of cavities or wells ll extending from the upper end of the block to points adjacent the lower end thereof, and with their axes parallel with the conical face of the black and converging in the direction of the shaft S.

The cavities or wells H are preferably pro-- vided by drilling the block which during such operation is solid throughout. In order to substantially reduce the weighth of the rotor while retaining sufficient strain resisting properties thereof, the block is materially reduced in. weight by, removing; a sub tanti l volume zpi its material after having provided the wells H therein. in the removal of the material, it is highly mportant that the rotor retain its balanced redri've s'haft, and the remaining stand'the strain occasioned by centrifugal force aridithfitrlfliehtlibesibe so supported as not to be subject ,to, breakage under centrifugal force.

While the rotor may be substantially reduced in weight by the removabofportions of its material infthe' provision of voids in differentways, intensive experimentation I has shown"-'lf1owever that the most satisfactory way is in'tlidrrhoval of thin sections of the material for uniformthickness in vertically-spaced relation eeetmrre tially'of theblock in the'provision o'ff'v'rtically spaced 7 circumferential flang es, web's'f'ori-fi'ns I 2 with interj/eningslots or voids [3'bf's'ul5stafntia1ly V the same thickness as that offtlie fins.

' 'fl he central portionill of thlbl oclsi'r elrnains result actsza's .a, guardin the event oL-breakageof the A rotor as well as avacuumreceptacleforthe rotor. ,The, rotor is ,dr veniby are ativel li tw t shaft S which is connected withsuitable, driving meansiand illustrated as ,an air .turbineiT- carried by .the chamber covenCLanda plate ,P supported tliereabove.v The.v cover,-.,turbine androtorare vertically movable on guide rods R through the instrumentalityvoft bars 13.

In. Fig. 1 the rotor -'s shown .ingraised, or. inoperative position and with tubes in serted therein. lPrior to the starting of alcentrifugating operation, the rotor is-lowered -byv-means ;of b, B'iinto the chamber until the. cover; engages the gtop of the chamber; The cover. is ,then secure'd Lin-position as .by means, of bolts engageable in, the tapped holes ,,hin,the, top of, of. the.chamberwaILM A vacuum is then provided in the chamber through connection c and the rotor is then set into rota; tion lby means ofthe powersourceflfe The present invention pertains particularly to the rotor construction; ;-w,hich; asr.is, mone clearly 7 5 shown in Figs. 2 and 3 consists of a metal block ere suifi' ieni t le. St ength qlidl enir l. er a ir Expe iment? th. frrbr s o o he. m:

prq ed oi r. h re nv d sc o h s air h tubes'and withstand the strain occ trifu e fo g rla d th t by .pm i j 1w s b t nt ally t e e th kn relatee rv be t t iens qfltli tu es ar ported and will not become brokerinnder the centrifugaljorcer,

ew s waterline the substance. conaining tubes QIS o f, stainles s steel or dural, arid. such each-proce d wii ie erub r a h t a e rid 8sneeg eb :Wiiht hne,l of the tube beyond a h'e ia on, the nut serving to dr v one luii e neae 919M1 e's i si' z' rm ni-"fin u andflange;iacilitate application and removal of the nut t a liremyieeiiebem as.

. pontrary to the general pr ticeleretofpre in in an nd a v wellsll, he -12 i iqn l ft I a-erased eug f b 'fi sun e t is sireniheqi b eili wli the wr lrtheaeri he are substant al f the preseat mtqr be g 5, un las mm ,ters and their lids reduced inertia ofthe present rotor the accelerawi in possible with the prior rotors.

By the provision of the individually covered tubes, same can be filled with the substance to be centrifugated since there is no actual flow of any liquid taking place in the tubes and thus the capacity of the tubes is substantially increased, since the open ended tubes in the old form rotor contained about cc. of substance, while the present closed tubes contain about 16 cc. of substance which in addition to the substantial reduction in time for acceleration and deceleration is a material factor in the centrifugating operation.

The invention further provides a simplified form of chuck or releasable connection between the rotor body and the drive shaft as well as the location of such connection nearer the center of mass of the metal block whereby providing for less vibration and smoother running of the rotor.

As indicated in Fig. 2, such chuck comprises a hexagon headed nut 2| and a steel collet 22. The nut is provided with an axial aperture 23 for reception of the shaft S, and the threaded portion 24 thereof threads into the internally threaded hole 25 opening into the upper end of the central solid portion M of the block and extending a substantial distance thereinto. The lower end of hole 25 communicates with the upper end of a frusto-conical recess 26 in which the correspondingly shaped body portion of the collet 22 rests.

The collet is provided with a central aperture 21 and is split throughout its length as at 28 for contraction and expansion thereof. The nut 2| is provided with a slot 29 which receives the head 30 of the collet. Thus, upon inserting the lower end of the shaft S within the aperture in the collet and turning the nut 2i inwardly, the shaft is firmly gripped and held in driving connection with the rotor.

From an inspection of Fig. 2 it will be seen that the gripped end of the shaft S is disposed a substantial distance Within the block or below the top end thereof, or substantially nearer the center of mass of the block than if disposed on a cover or the upper end of the block as in prior constructions, whereby providing a better balanced driving connection.

Experimentation has shown, however, that the shaft driving connection should not be located beyond one-third of the distance from the top to the bottom of the block for the reason that if the central solid portion I4 be too deeply pierced the tensile strength of the rotor will not be sufiicient to Withstand the strain under centrifugal force occasioned by the high speed of rotation of the rotor.

Many advantages of the improved construction herein disclosed should be appreciated from the foregoing disclosure, principal ones of which are are follows:

1. Lighter weight with consequent less inertia and shorter acceleration and deceleration 'periods;

2. Increased capacity by the utilization of closed tubes completely filled with the substance to be centrifugated;

3. Suspension point of drive shaft nearer the center of mass or gravity withless vibration and smoother running of: the rotor. V

While I have disclosed my invention in accordance with a single specific embodiment thereof, such is to be considered as illustrative only, and not restrictive, the scope of the invention being defined in the subjoined' claims.

WhatI claim is:

1. A rotor for ultra-centrifugating machines comprising a block of generally frusto-conical form having its smaller endupward, said'blo'ck comprising a central solidportion and vertically spaced circumferential fins extending normal to the axis of the rotor from the central portion between the upper and lower ends of the block, and tube receiving wells in the block adjacent to and parallel with its conical wall and extending in part through said fins.

2. A rotor according to claim 1 wherein said fins occupy the major distance between the upper and lower ends of the block and extending inwardly beyond the innermost walls of the wells, and wherein said fins are relatively narrow and are separated by voids of substantially the same width.

3. A rotor for ultracentrifugating machines, comprising a block of generally frusto-conical form having its smaller end upward, a plurality of tube supporting wells in said block opening through the upper end thereof and disposed adjacent the conical walls with their axes parallel therewith, and vertically spaced weight reducing slots extending circumferentially of the block, said slots intersecting the wells and opening through the conical wall of the block providing intervening fin-like portions extending normal to the axis of the rotor.

4. A rotor for ultracentrifugating machines, comprising a block of generally frusto-conical form having its smaller end upward, said block including a solid axial portion of substantial radius and a plurality of horizontal disposed vertically spaced fins extending normal to the axis of the solid portion to the conical outer wall of the block, and a plurality of tube supporting wells parallel with said conical wall and extending through said fins.

5. A rotor for ultracentrifugating machines, comprising a body of generally frusto-conical form having its smaller end upward, said body including a substantially solid cylindrical axial central portion, a vertical series of circumferential weight reducing slots in thebody outwardly of said solid axial portion providing annular radiating fins of increasing diameters therebetween extending normal to the axis of the rotor to the conical outer surface, said fins having registering apertures at circumferentially spaced points providing a plurality of tube supporting wells in the body adjacent to and parallel with its conical outer surface, and means for releasably supporting the end of a drive shaft disposed axially Within said solid portion.

6. A rotor for ultra-centrifugating machines, comprising a block of generally frusto-conical form having its smaller end upward, a plurality of tube supporting wells in said block opening through the upper end thereof and disposed adjacent the conical wall with their axes parallel therewith, and a vertical series of circumferentially disposed slots in the block providing intervening fins extending normal to the axis of the rotor, and slots intersecting the wells therein for substantially reducing the weight of the block 

